Lithium-doped silicon oxide composite anode material with high initial coulombic efficiency and preparation method thereof

Abstract

A lithium-doped silicon oxide composite anode material with high initial Coulombic efficiency and a preparation method are provided, which relates to the field of anode materials for lithium batteries. The material includes nano-silicon, lithium silicate and a conductive carbon layer. A diffraction peak intensity of Li 2 Si 2 O 5 (111) with 2θ being 24.7±0.2° in an XRD pattern of the lithium-doped silicon oxide composite anode material is I1, a diffraction peak intensity of Li 2 SiO 3 (111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25. The material provided in the present invention has a specific phase composition ratio, thereby achieving the effect of high initial Coulombic efficiency and high specific capacity.

What is claimed is: 
     
         1 . A lithium-doped silicon oxide composite anode material, comprising nano-silicon, lithium silicate and a conductive carbon layer, wherein a diffraction peak intensity of Li 2 Si 2 O 5 (111) with 26 being 24.7±0.2° in an XRD pattern of the lithium-doped silicon oxide composite anode material is I1, a diffraction peak intensity of Li 2 SiO 3 (111) with 2θ being 26.8±0.3° in the XRD pattern is I2, and I1/I2<0.25. 
     
     
         2 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein I1/I2<0.15. 
     
     
         3 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein I1/I2<0.05. 
     
     
         4 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein a diffraction peak area of Li 2 SiO 3 (111) with 2θ being 26.8±0.3° in an XRD pattern of the lithium-doped silicon oxide composite anode material is A1, and a diffraction peak area of Si(111) with 2θ being 28.4±0.3° in the XRD pattern is A2, and A2/A1≥1.0. 
     
     
         5 . The lithium-doped silicon oxide composite anode material according to  claim 4 , wherein A2/A1≥1.3. 
     
     
         6 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein the lithium-doped silicon oxide composite anode material has a core-shell structure comprising a core and a shell, the core comprises the nano-silicon and the lithium silicate, the lithium silicate comprises either or both of Li 2 SiO 3  and Li 2 Si 2 O 5 , and the shell comprises the conductive carbon layer distributed on a surface of the core. 
     
     
         7 . The lithium-doped silicon oxide composite anode material according to  claim 6 , wherein the shell further comprises a water-resistant coating. 
     
     
         8 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein, with a total mass of the lithium-doped silicon oxide composite anode material being 100 wt %, a mass percentage of a carbon material is 0.5 wt % to 10 wt %. 
     
     
         9 . The lithium-doped silicon oxide composite anode material according to  claim 8 , wherein the carbon material comprises a coated carbon in a silicon oxide SiO x  and a coated carbon in a water-resistant coating, and a content of the coated carbon of the water-resistant coating is 0.5 wt % to 4 wt % of the lithium-doped silicon oxide composite anode material. 
     
     
         10 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein the nano-silicon is elemental silicon, and an average grain size of the nano-silicon is in a range of 3 nm to 20 nm. 
     
     
         11 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein a particle size D50 of the lithium-doped silicon oxide composite anode material is in a range of 2 μm to 15 μm, and a particle size D90 of the lithium-doped silicon oxide composite anode material is in a range of 5 μm to 25 μm. 
     
     
         12 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein an initial Coulombic efficiency at 0.8V cutoff potential of the lithium-doped silicon oxide composite anode material is greater than 84%. 
     
     
         13 . The lithium-doped silicon oxide composite anode material according to  claim 1 , wherein a reversible specific capacity at 0.8V cutoff potential of the lithium-doped silicon oxide composite anode material is greater than 1300 mAh/g. 
     
     
         14 . A preparation method of the lithium-doped silicon oxide composite anode material according to  claim 1 , comprising steps of:
 S1, mixing a silicon oxide SiO x , a lithium source with a Li 2 SiO 3  nucleating agent by a solid-phase mixing mode to form a pre-lithiated precursor;   S2, carrying out heat treatment on the pre-lithiated precursor under a vacuum or non-oxidizing atmosphere, and then depolymerizing and screening the pre-lithiated precursor to obtain a compound powder; and   S3, carrying out impurity removal and modification on the compound powder formed in Step S2 to obtain a lithium-doped silicon oxide composite anode material.   
     
     
         15 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein, by mass fraction, 100 parts of the silicon oxide SiO x , 5 to 20 parts of the lithium source, and 0.02 to 1 part of the Li 2 SiO 3  nucleating agent are included. 
     
     
         16 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein the Li 2 SiO 3  nucleating agent comprises a rare earth metal oxide. 
     
     
         17 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein the Li 2 SiO 3  nucleating agent comprises at least one of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide and yttrium oxide. 
     
     
         18 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein in the silicon oxide SiO x , 0.7≤x≤1.3. 
     
     
         19 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein the silicon oxide SiO x  is uncoated with carbon. 
     
     
         20 . The preparation method of the lithium-doped silicon oxide composite anode material according to  claim 14 , wherein the silicon oxide SiO x  is coated with carbon by either of gas-phase coating and solid-phase coating, and a mass percentage of a coated carbon in the silicon oxide SiO x  is 0.1% to 6%.